Final answer:
Absolute humidity is the actual amount of water vapor present in a mixture of air and water, measured in grams per cubic meter of air. It differs from relative humidity, which is a ratio and varies with temperature. The concept of absolute humidity is important in understanding how much moisture air can contain at any given point.
Step-by-step explanation:
Absolute humidity is B. The actual amount of the water vapour in a mixture of air and water. This is a measure of the water vapor content in the air regardless of the air's temperature. Unlike relative humidity, which is the ratio of the current amount of water vapor to the maximum amount that air can hold at a given temperature, absolute humidity is expressed in grams of water per cubic meter of air (g/m³). When discussing the capacity of air to hold water vapor, it's essential to understand that warmer air can contain more moisture than cooler air before becoming saturated.
For example, if the air contains 9.40 g/m³ of water vapor, and this amount represents saturation at 10.0°C, then the relative humidity at that temperature is 100%, and 10.0°C would be the dew point for that air. If the temperature increases, the air can hold more water vapor, and the relative humidity would decrease unless additional moisture is added to the air.